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Outta Gas (From the 2007: Exploring the Inner Space of the Celebes Sea 2007: Exploring the Inner Space of the Celebes Sea Outta Gas FOCUS MAXIMUM NUMBER OF STUDENTS Gas laws 30 GRADE LEVEL KEY WORDS 9-12 (Chemistry/Physics) Celebes Sea SCUBA diving FOCUS QUESTION Gas laws How can Boyle’s Law, Charles’ Law, Gay-Lussac’s Ideal Gas Law Law, Henry’s Law, and Dalton’s Law be used to Boyle’s Law predict the behavior of gases used in SCUBA div- Charles’ Law ing? Gay-Lussac’s Law Henry’s Law LEARNING OBJECTIVES Dalton’s Law Students will define Boyle’s Law, Charles’ Law, Pressure Gay-Lussac’s Law, Henry’s Law, and Dalton’s Law. Worksheet Mathematics Students will use Boyle’s Law, Charles’ Law, Gay- Lussac’s Law, Henry’s Law, and Dalton’s Law to BACKGROUND INFORMATION solve practical problems related to SCUBA diving. Indonesia is well-known as one of Earth’s major centers of biodiversity. Although Indonesia cov- MATERIALS ers only 1.3 percent of Earth’s land surface, it “Blue Water Diving Worksheet,” one copy for includes: each student or student group • 10 percent of the world’s flowering plant species; AUDIO/VISUAL MATERIALS • 12 percent of the world’s mammal species; None • 16 percent of all reptile and amphibian species; and TEACHING TIME • 17 percent of the world’s bird species. One or two 45-minute class periods plus time for students to complete worksheet In addition, together with the Philippines and Great Barrier Reef, this region has more species SEATING ARRANGEMENT of fishes, corals, mollusks, and crustaceans than Classroom style any other location on Earth. 1 2007: Exploring the Inner Space of the Celebes Sea – Grades 9-12 (Chemistry/Physics) Focus: Gas laws oceanexplorer.noaa.gov What, exactly, is meant by biodiversity, and why of the ocean. Note that the term “midwater” as is it important? The term “biodiversity” is usually used here includes the entire water column, but understood to include variety at several levels: the same term has also been used to refer to • variety of ecosystems: high biodiversity sug- only part of the water column. Scientists often gests many different ecosystems in a given divide the ocean water column into three zones: area; the “epipelagic zone” (also called the “sunlit” or • variety of species: high biodiversity suggests “euphotic” zone) from the surface to a depth of many different species in a given area; about 200 m; the “mesopelagic zone” between • variety of interactions between species; and 200 m and 1100 m; and the “bathypelagic • variety within species (genetic diversity): high zone,” which is deeper than 1100 m. biodiversity suggests a relatively high level of genetic variety among individuals of the same “Plankton” is a general term for organisms that species. drift or swim weakly in midwater environments, and includes plants (phytoplankton) as well as A simple definition of biodiversity could be “The animals (zooplankton). Phytoplankton include variety of all forms of life, ranging in scale from major primary producers in aquatic food webs, genes to species to ecosystems.” and zooplankton are often the primary consum- ers that are a key link in transferring energy to Biodiversity is important to humans because our other consumers in these food webs. Despite their survival depends upon many other species and importance, many types of zooplankton are not ecosystems. Some examples of our dependence well-understood. This is partially because many on biodiversity include: zooplankton are fragile, jelly-like creatures that • fresh air containing oxygen; are easily damaged by nets and other devices • clean water; that are traditionally used to collect midwater • productive soils; animals for study. Scientists participating in the • food, medicines and natural products; 2007: Exploring the Inner Space of the Celebes • natural resources that provide the basis for Sea Expedition plan to use techniques known as human economies; and blue-water diving to observe and collect fragile • natural beauty that improves our quality of midwater animals. life. (adapted from the Biodiversity Project, http://www. Diving in the open ocean is quite different from biodiversityproject.org/bdimportant.htm) nearshore diving, because there are no objects for visual reference, and it is very easy for divers Quite a lot is known about Indonesia’s terres- to become disoriented. Blue-water diving tech- trial and shallow-water ecosystems. But scientific niques involve a system of lines and floats to cre- knowledge and understanding of midwater ate visual reference points, as well as procedures ocean communities is generally sketchy, and that help keep divers in touch with each other. many midwater animals have not been studied One diver (called the “safety diver”) holds an at all – even though the midwater ocean environ- aluminum “trapeze,” and descends to the desired ment is our planet’s largest ecosystem. Midwater depth along a weighted line attached to a sur- animals range from microscopic zooplankton to face float. Other divers are attached to safety the largest animals on Earth, provide a major lines that clip onto the trapeze. This system allows source of nutrition for benthic (bottom) communi- the safety diver to keep track of the “working” ties, and are an important link in the transfer of divers who are free to concentrate on research energy and materials from the top to the bottom tasks. 2 2007: Exploring the Inner Space of the Celebes Sea – Grades 9-12 (Chemistry/Physics) oceanexplorer.noaa.gov Focus: Gas laws that they are familiar with the system of units to Even with such specialized techniques, divers be used. The appropriate SI units are: who use self-contained underwater breathing • pressure in pascals (Pa) apparatus (SCUBA) still must be aware of be • volume in cubic meters (m3) behavior of gases under pressure, and how the • number of molecules in moles (mol) basic gas laws apply to SCUBA diving. In this • temperature in degrees Kelvin (°K) lesson, students will be introduced to Boyle’s Law, • R has a value of 8.314 joules per mole per Charles’ Law, Gay-Lussac’s Law, Henry’s Law, degree Kelvin (j/mol/°K) and Dalton’s Law, and how these laws affect SCUBA divers. However, other units are commonly used when gas laws are applied to SCUBA diving: LEARNING PROCEDURE • pressure in pounds per square inch (psi) or 1. To prepare for this lesson, review the introduc- atmospheres (atm); 1 atm = 101,325 Pa = tory essays for the 2007: Exploring the Inner 14.7 psi Space of the Celebes Sea Expedition at http:// • volume in liters or cubic feet; 1 l = 10-3 m3; 1 oceanexplorer.noaa.gov/explorations/07philippines/. You can ft3 = 28.3 l view many images of planktonic organisms at • R has a value of 0.082 L · atm/mol/°K http://www.imagequest3d.com/catalogue/larvalforms/, but be aware of copyright restrictions posted on the Students should also understand that when the Web site. Ideal Gas Law is used to describe the behavior of a fixed quantity of gas, the equation can be If students are not familiar with the fundamental written as concepts embodied in Boyle’s Law, Charles’ P1 • V1 = P2 • V2 Law, Gay-Lussac’s Law, Henry’s Law, and T1 T2 Dalton’s Law, you may want to introduce these concepts using activities described in the “It’s Where P1, V1, and T1 are the initial pressure, the Law!” lesson. volume, and temperature, respectively, and P2, V2, and T2 are the pressure, volume, and tem- 2. Briefly introduce the 2007: Exploring the Inner perature after one or more of these variables Space of the Celebes Sea Expedition, focusing has changed. on the importance of midwater animals and why these animals have not been well-studied. 4. Provide each student or student group with a You may want to briefly describe the problems copy of “Blue Water Diving Worksheet.” When of SCUBA diving in the open ocean and some students have solved the Worksheet problems, of the blue-water diving techniques used to lead a discussion of their answers. The follow- overcome these problems. ing points should be included: 3. Discuss the Ideal Gas Law (P • V = n • R • (1) Boyle’s Law states that the product of the T). Students should recognize that this “law” volume and pressure of a gas held at a con- describes the interaction between four vari- stant temperature is equal to a constant (PV ables: pressure, volume, number of gas mole- = k). So, if the pressure of the gas doubles, cules, and temperature. Be sure students under- the volume will be decreased by half; and stand that “pressure” refers to absolute pressure if the volume of a gas doubles, the pressure (in the case of SCUBA diving, the combined must decrease by half. pressure of the atmosphere and water), and 3 2007: Exploring the Inner Space of the Celebes Sea – Grades 9-12 (Chemistry/Physics) Focus: Gas laws oceanexplorer.noaa.gov (2) Charles’ Law states that the volume of a partial pressure of oxygen in the lungs can given amount of gas is directly propor- cause loss of consciousness known as “deep- tional to the Kelvin temperature provided water blackout.” the amount of gas and the pressure remain fixed. (8a) When she takes a breath at 20 m, the air in her lungs has a pressure of 3 atm. (3) Gay-Lussac’s Law states that for a fixed amount of gas (fixed number of moles) at a (8b) The volume of air in her lungs when she fixed volume, the pressure of the gas is pro- takes a deep breath at 20 m is 5 liters. portional to the temperature. (8c) If she took a deep breath and returned to (4) Henry’s Law states that the mass of a gas the surface while holding her breath, the which dissolves in a volume of liquid is pro- volume of air in her lungs would expand by portional to the pressure of the gas.
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